Initialize some missing vulkan function pointers Those methods are used by VMA. However VMA can get those methods by itself, if null function pointers are provided for creating the VMA. But it will cause problem, when ANGLE & Chromium are sharing one VMA implementation, since the VMA implementation in chromium will be built with VMA_STATIC_VULKAN_FUNCTIONS=0 & VMA_DYNAMIC_VULKAN_FUNCTIONS=0. Bug: chromium:1170339 Change-Id: I5bf435698e4e361bfa7a6afce84390ccc4355b53 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2655795 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>